Lighting device and method for manufacturing a lighting device

ABSTRACT

A lighting device for providing decorative lighting is disclosed. In one embodiment, the lighting device comprises a base, said base comprises a base for retro-fitting a traditional incandescent light bulb, a continuous optical element in which a string of a plurality of light emitting diodes is arranged, and an envelope encapsulating said continuous optical element such that the lighting device resembles a traditional incandescent light bulb.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a continuation of U.S. Ser. No. 14/987,369, filedJan. 6, 2016, which is a continuation of U.S. Ser. No. 13/996,778, filedJun. 21, 2013 which is the U.S. National Phase application under 35U.S.C. § 371 of International Application No. PCT/IB2011/055565, filedDec. 9, 2011, which claims the benefit of European Application No.10196396.5, filed Dec. 22, 2010. These applications are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to the field of lightingdevices.

BACKGROUND OF THE INVENTION

Traditional incandescent light bulbs are available in various designssuch as plain functional bulbs with different glass finishes (e.g.transparent, diffuse or colored) and decorative bulbs with complexfilaments, wherein the filament itself serves a decorative purpose.However, due to demands on power saving in lighting devices, driven byeco awareness and legislation, traditional incandescent light bulbs arebeing replaced by more power efficient light sources such as fluorescentlamps and LED (light emitting diode) lamps. Such conventionaleco-friendly lamps do not provide the same various designs astraditional incandescent light bulbs.

A solution of how to provide a lighting device resembling a carbonfilament lamp is disclosed in WO 2006/035349. The document shows alighting device comprising a solid state light source optically coupledto an optical fiber having an out-coupling surface. A drawback with sucha lighting device is that it does not provide a sufficientlyenergy-efficient functional lighting (such as e.g. general lighting ortask lighting).

SUMMARY OF THE INVENTION

Thus, there is a need for providing alternatives and/or new devices thatwould overcome, or at least alleviate or mitigate, at least some of theabove mentioned drawbacks. It is with respect to the aboveconsiderations that the present invention has been made. An object ofthe present invention is to provide an improved alternative to the abovementioned technique and prior art.

More specifically, it is an object of the present invention to provide alighting device enabling both decorative lighting and functionallighting with improved efficiency. It is also an object of the presentinvention to provide a method of manufacturing such a lighting device.

These and other objects of the present invention are achieved by meansof a lighting device and a method of manufacturing the lighting devicehaving the features defined in the independent claims. Preferableembodiments of the invention are characterized by the dependent claims.

Hence, according to a first aspect of the present invention, a lightingdevice is provided. The lighting device comprises a first light emittingelement being optically coupled to a light guide having an out-couplingsurface for illumination via the light guide. Further, the lightingdevice comprises a second light emitting element dedicated for directillumination from the lighting device.

Further, according to a second aspect of the invention, a method ofmanufacturing a lighting device is provided. The method comprises thesteps of providing a first light emitting element, providing a lightguide having an out-coupling surface, and optically coupling the firstlight emitting element to the light guide. Further, the method comprisesthe step of providing a second light emitting element dedicated fordirect illumination from said lighting device.

The basic idea of the invention is that the light emitted from the firstlight emitting element is emitted out of the lighting device via thelight guide and the light emitted from the second light emitting elementis emitted out of the lighting device directly from the second lightemitting element. As a result, decorative lighting is provided by thelight guide and the first light emitting element, and a directillumination (suitable for functional lighting) is provided by thesecond light emitting element.

In this respect, with the term “direct illumination” it is meant thatmost of, or at least a considerable part of the light emitted from thesecond light emitting element is emitted from the lighting devicewithout passing a light guide. The inventor has realized that thelighting device according to prior art suffers from energy-losses whenthe light emitted from the solid state light source is coupled into theoptical fiber and then out again. Hence, the lighting device accordingto prior art may be improved with respect to functional lighting (suchas e.g. general lighting or task lighting). Functional lighting may bedefined as a type of lighting wherein it is desirable to output from thelighting device as much of the light emitted from the solid state lightsource as possible.

The present invention is advantageous in that the lighting deviceprovides both a decorative appearance (look) and functionalillumination, and is still energy-efficient since the light emitted fromthe second light emitting element is directly emitted from the secondlight emitting element without unnecessary energy-loss.

Further, the present invention is advantageous in that a doublefunctionality (decorative lighting and functional lighting) is providedwithin a single lighting device, enabling an extended field of use sincethe lighting device may be used both in a decorative purpose and e.g.for general lighting or task lighting.

According to an embodiment of the present invention, the illuminationfrom the lighting device via the light guide and the first lightemitting element may be dedicated to a first type of lighting. Further,illumination from the lighting device from the second light emittingelement without any light guide may be dedicated to a second type oflighting. Accordingly, the first type of lighting and the second type oflighting are functionally and structurally separated such that each typeof lighting can be optimized in terms of energy-efficiency.

According to an embodiment of the present invention, the first lightemitting element may be dedicated to decorative lighting (via the lightguide, i.e. the first type of lighting as defined in the precedingembodiment) and the second light emitting element may be dedicated tofunctional lighting (without any light guide, i.e. the second type oflighting as defined in the preceding embodiment).

According to an embodiment of the present invention, the light intensityof the second light emitting element may be adjustable relative to thelight intensity of the first light emitting element. Preferably thelight intensity of the second light emitting element may be adjustablerelative to the light intensity of the first light emitting element inresponse to an input signal to the lighting device. The input signal maybe received at the lighting device from a dimmer connected to thelighting device (wherein the actual receiver of the dim signal is on themains voltage). Alternatively, the input signal may be received at e.g.a low voltage circuitry of the lighting device (further described below)via a remote control (operated by a user of the lighting device).Preferably, a transfer function may be used such that the input voltageis correlated to a specific relationship or ratio between the intensityof the first light emitting element and the intensity of the secondlight emitting element. The present embodiment is advantageous in thatit provides at least two different operation modes of the lightingdevice, a decorative mode for which the light intensity of the secondlight emitting element is lower than the light intensity of the firstlight emitting element and a functional mode for which the lightintensity of the second light emitting element is higher than the lightintensity of the first light emitting element. In other words, the lightguide will become more visible and stand for a greater part of the totallight-output from the lighting device when the light intensity of thesecond light emitting element is lowered in the decorative mode comparedto when the lighting device is in the functional mode. In the functionalmode, the light intensity of the second light emitting element willdominate the total light-output from the lighting device.

In an embodiment of the present invention, at least one of the secondlight emitting element and the first light emitting element may bedimmable, which is advantageous in that it provides a step-lesstransition between the two above-mentioned operation modes of thelighting device. Moreover, the first light emitting element and thesecond light emitting element may be simultaneously and/or separately(individually) dimmed. For example, when the light intensity of thefirst light emitting element is increased, simultaneously, also thelight intensity of the second light emitting element may be increased.Such a kind of regulation may be implemented using a single dimmingdevice common to all light emitting elements (making the lighting devicerelatively technically simple). Hence, when both the first lightemitting element and the second light emitting element are operated at alow dimmed level (i.e. at a low light intensity) the total light-outputfrom the lighting device is low, thereby rendering visible the lightguide which may provide a decorative appearance. In contrast, when thelight emitting elements are driven at a high power level (i.e. at a highlight intensity) the total light-output from the lighting device ishigh, thereby providing a functional lighting. It will be appreciatedthat such a kind of regulation with a common dimmer resembles thefunction of a traditional incandescent lighting device.

According to another example, wherein the light emitting elements areindividually dimmed, the light intensity of the first light emittingelement is increased while the light intensity of the second lightemitting element is decreased. The above-mentioned effects (forresemblance to the function of a traditional incandescent lightingdevice) may be achieved and even enhanced, when the first light emittingelement and the second light emitting element have different lightintensities.

According to an embodiment of the invention, a wavelength (color) of thelight emitted from the first light emitting element is adjustable,preferably in response to an input signal to the lighting device. Forexample, the color of the first light emitting element may be adjustedto be red/amber in the decorative mode and yellow/white in thefunctional mode.

In an embodiment of the invention, the input signal to the lightingdevice may be a current or a voltage supplied to the lighting device.Further, lighting device may comprise a circuitry with a transferfunction correlating the input signal with a light-output and/or thelight color of the first and second light emitting element. As anillustrating example, for a low input signal (such as in a dimmedtraditional incandescent lamp), the first light emitting element mayprovide a red/amber color and have a relatively low light intensity,while the light intensity of the second light emitting element maypreferably be turned off. The stronger the input signal is, the more thefirst light emitting element may become yellow/white (and the more thelight output from the first light emitting element is increased) and, atsome threshold value of the input signal, the second light emittingelement switches on and light-output is slowly increased.

According to further embodiments of the present invention, the lightguide may comprise an optical fiber, which is advantageous in that theoptical fiber may resemble a carbon-filament. Alternately, the lightguide may comprise a light guide plate, which may be designed in anydesired way. For example, the light guide may be designed in anythree-dimensional shape.

According to an embodiment of the present invention, the light guide maybe provided with diffusing means for out-coupling light. The diffusingmeans enhances the out-coupling of the light guided into the light guideand thus, renders the light guide more clearly visible. In an embodimentof the invention, the structure of the out-coupling surface (e.g. theroughness of the surface) may be selected to adjust the scattering ofthe light. Further, the light guide may comprise (scattering ordiffusing) particles and/or vacuum/gas bubbles for out-coupling light.In other words, distortions of the optical characteristics of the lightguide are provided for scattering out some of the light. Thesedistortions may be located on the surface/edge of the light guide and/orinside of the light guide. Generally, any optical distortion resultingin a change of the internal light angles may result in that part of thelight is coupled out of the light guide. Distortions in a 3D-shapedlight guide may for example be obtained by local laser heating.

According to an embodiment of the present invention, at least one of thefirst light emitting element and the second light emitting element maycomprise at least one light emitting diode (LED), which is advantageousin that LEDs are high-efficient point-like light sources available inseveral different colors, thereby allowing various designs of thelighting device. Further, the LED may be a laser-LED, which isadvantageous in that it improves the coupling of light to the lightguide.

According to an embodiment of the invention, a string of a plurality oflight emitting diodes may be provided in the light guide.

According to an embodiment of the present invention, the lighting devicemay further comprise an envelope encapsulating the first light emittingelement, the second light emitting element and the light guide, which isadvantageous in that the light emitting elements and the light guidewill be protected against damage and dust. Additionally, the lightingdevice will resemble a traditional incandescent light bulb.

According to an embodiment of the present invention, the lighting devicemay further comprise a base at which the first light emitting elementand the second light emitting element are arranged.

Optionally, the lighting device may further comprise adiffusing/scattering element arranged on top of the second lightemitting element e.g. in the form of a plate covering the second lightemitting element(s). Such a diffusing/scattering element is advantageousin that an individual light emitting element will be less visible andprovide a more even light distribution than without adiffusing/scattering element.

Further objectives of, features of, and advantages with, the presentinvention will become apparent when studying the following detaileddisclosure, the drawings and the appended claims. Those skilled in theart realize that different features of the present invention can becombined to create embodiments other than those described in thefollowing. In particular, it will be appreciated that the variousembodiments described for the lighting device are all combinable withthe method as defined in accordance with the second aspect of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of thepresent invention, will be better understood through the followingillustrative and non-limiting detailed description of preferredembodiments of the present invention, with reference to the appendeddrawings, in which:

FIG. 1 shows a lighting device according to an embodiment of the presentinvention;

FIG. 2 shows a light guide according to an embodiment of the presentinvention;

FIG. 3 shows a light guide according to another embodiment of thepresent invention; and

FIG. 4 is a general outline of a method of manufacturing a lightingdevice according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

With reference to FIG. 1, there is shown a lighting device in accordancewith an embodiment of the present invention.

FIG. 1 shows a lighting device 1 comprising a first light emittingelement 101 and a second light emitting element 102. The first lightemitting element 101 is optically coupled to a light guide 110 having anout-coupling surface 111. The optical coupling can be provided e.g. viaan optical element (not shown) arranged between the first light emittingelement 101 and the light guide 110 or by linking the first lightemitting element 101 directly to the light guide 110, as shown in FIG.1.

Optionally, the lighting device may be provided with additional firstlight emitting elements being optically coupled to the light guide 110.For example, one first light emitting element may be coupled to a firstend of the light guide 110 and another first light emitting element maybe coupled to another end of the light guide 110 (opposite to the firstend).

Further, the lighting device may be provided with additional secondlight emitting elements 102 for providing functional lighting.

The first light emitting element 101 and/or the second light emittingelement 102 may for instance be light emitting diodes, LEDs, such ase.g. laser LEDs. For example, an amber colored LED, providing a warmlight, may be used as the first light emitting element 101, therebyresulting in a light guide resembling a warm glowing filament (when thefirst light emitting element is activated/on). An alternative is toprovide e.g. phosphor (or any other wavelength converting material) ontop of the light guide (i.e. at the out-coupling surface of thelightguide) and select a phosphor providing a warm colored light.According to another example, the first light emitting element 101 maycomprise a red LED, a green LED and a blue LED, thereby togetherproviding a white light, which may be modulated into different colors bycontrolling the red, green and blue LED.

Further, an LED of a colder color (which may be more efficient), such aswhite, may be used as the second light emitting element 102, therebyproviding light being suitable for functional lighting. According toanother example, the second light emitting element 102 may comprise ared LED, a green LED and a blue LED, thereby together providing a whitelight, which may be modulated into different colors by controlling thered, green and blue LED. However, it will be appreciated that theinvention is not limited to such color configuration, the light emittingelements 101, 102 in the lighting device may be of any desired color.

The light guide 110 may comprise an optical fiber (like an optical waveguide) made of a suitable material such as plastics or glass-fiber. Theuse glass-fiber material is advantageous because of its optical qualityand material characteristics (e.g. sensitivity to heat). The opticalfiber may be of a shorter or longer length allowing a simple or morecomplex design. For example, the optical fiber may be spirally wound inorder to resemble a traditional retro-filament.

The out-coupling of light from the out-coupling surface 111 of the lightguide 110 may be achieved (and/or enhanced) in different ways. Some ofthe light may be out-coupled due to curvatures of the light guide 110.Moreover, the light guide 110 may be provided with diffusing means forout-coupling the light. In general, any optical distortion added to thelight guide will provide out-coupling of light. The diffusing means maybe provided e.g. by making the out-coupling surface 111 rough (e.g. bysand-blasting, scratching, or molding in a texture in the surface), orby providing indents or small protrusions in the out-coupling surface111. Further, particles (e.g. white paint) and/or vacuum/gas bubbles(e.g. created by local laser heating) may be provided on or inside thelight guide such that light is scattered out of the light guide.

According to an embodiment of the present invention, the light guide 110may comprise at least one connecting port 112 to which the first lightemitting element 101 may be optically coupled. The present embodiment isadvantageous in that it allows a great part of the light emitted fromthe first light emitting element 101 to be received and out-coupled bythe light guide 110, thereby serving a decorative purpose, and still agreat part of the light emitted from the second light emitting element102 provides an illumination without unnecessary considerableenergy-losses in any light guide.

However, some (i.e. a relatively small part) of the light emitted fromthe second light emitting element(s) 102 may be coupled into the lightguide 110 via the out-coupling surface 111, and thus, coupled out againvia the out-coupling surface 111, thereby contributing to theillumination out of the light guide 110.

With reference to FIG. 2, there is shown an alternative design of alight guide according to an embodiment of the invention. FIG. 2 shows alight guide in the form of a light guide plate 210 being opticallycoupled to a first light emitting element 201. Some of the light emittedfrom the first light emitting element 201 is coupled out via an edge 211which may be curved (and optionally rough), thereby resulting in theappearance of a filament such as in a traditional light bulbs. Further,light may be coupled out via diffusing means provided inside the lightguide plate 210 or on the surface of the light guide plate 210.

It will be appreciated that the light guide may be designed in anydesired three-dimensional shape, such as a spherical or prismatic shape.Further, the diffusing means may be provided at any desired position inor on the light guide. For example, the diffusing means may form apattern (such as a filament-resembling pattern).

With reference to FIG. 3, there is shown another design of a light guideaccording to yet another embodiment of the invention. FIG. 3 shows alight guide 320 in the form of a continuous optical element 323 in whicha string of a plurality of LEDs 321 is arranged. The LEDs 321 may bemounted on a small flexible PCB (printed circuit board) 322 with thecontinuous optical element 323 on top of it (or encapsulating it).

Turning again back to FIG. 1, further embodiments of the invention willbe described. The lighting device 1 may further comprise an envelope 130encapsulating the first light emitting element 101, the second lightemitting element 102 and the light guide 110. Preferably, the envelope130 is transparent (or at least semi-transparent) such that the lightguide 110 is visible for providing a decorative effect. Further, theenvelope 130 may be formed as a bulb resembling a traditionalincandescent light bulb. The lighting device 1 may further comprise abase 140 at which the first light emitting element 101 and the secondlight emitting element 102 are arranged. The base 140 may comprise abayonet base or a screw base 141 (e.g. of the type E14, E26 or E27),which is advantageous in that the lighting device can be fitted inconventional lamp fittings and used as a replacement for a traditionalincandescent light bulb (retro-fitting). The base 140 may furthercomprise a heat-sink 142 for cooling the light emitting diodes 101, 102.Optionally, the light emitting elements 101, 102 may be arranged suchthat an upper portion of the heat-sink 142 (or an upper portion of thebase 140) hides the light emitting elements 101, 102 (as shown inFIG. 1) for reducing the risk of direct view of them. Further, theinside of the upper portion of the heat-sink 142 may be reflective suchthat all (or at least almost all) light emitted from the light emittingelements 101, 102 can be output from the lighting device.

The lighting device may further comprise a diffusing/scattering element(not shown) in form of a plate on top of the second light emittingelements 102. For example, such plate may be arranged on top of the base140. The plate may be provided with a hole where light emitted from thefirst light emitting element 101 may go through to be coupled into thelight guide 110.

The lighting device 1 may further comprise electronic driving means 150provided with a power supply for converting the mains voltage supplyinto an output signal suitable for driving the light emitting elements101, 102. The electric driving means 150 may further comprise anelectronic circuitry configured to control the light intensity of thefirst light emitting element 101 and/or the second light emittingelement 102 such that the light intensity of the second light emittingelement 102 is adjustable relative to the light intensity of the firstlight emitting element 101. Further, the electronic circuitry may beconfigured to slightly modulate the brightness (or color) of the firstlight emitting element 101, or to sequentially switch on and off thefirst light emitting element 101, for providing a flame and flickeringeffect of the light guide 110. The electronic circuitry may furthercontain a transfer function for correlating an input signal (such asinput current or input voltage) with a light output and/or an emissioncolor of the first and second light emitting elements. The electricdriving means 150 may be controlled by a remote control unit, by buttonson the base 140 or by any other type of user interface.

In an embodiment of the invention, the first light emitting element 101and/or the second light emitting element 102 may be dimmable. In anembodiment of the invention, the lighting device supports traditionalincandescent light dimmers such that the light emitting elements canoperate in a dimmed mode.

With reference to FIG. 4, a method of manufacturing a lighting deviceaccording to an embodiment of the present invention will be described.FIG. 4 shows the general outline of a method 400 of manufacturing alighting device. The method comprises a step 410 of providing a firstlight emitting element, a step 420 of providing a light guide having anout-coupling surface, and a step 430 of optically coupling the firstlight emitting element to the light guide. Further, the method 400comprises a step 440 of providing a second light emitting elementdedicated for direct illumination from the lighting device.

While specific embodiments have been described, the skilled person willunderstand that various modifications and alterations are conceivablewithin the scope as defined in the appended claims.

For example, additional light guides with associated first lightemitting elements may be provided in the lighting device. Further, thelighting device can be applied in standalone retro-fit incandescent bulbreplacements as well as in dedicated new luminaries. Moreover, thelighting device is not limited to be designed as a conventional lightbulb. It can also be designed e.g. as a tubular-shaped lamp withconnectors at both ends of the tube.

1-20. (canceled)
 21. A light guide comprising: a string of a pluralityof light emitting diodes (LEDs), the LEDs being mounted on a flexibleprinted circuit board (PCB); and wherein the light guide is shaped as acontinuous optical element that encapsulates the string of a pluralityof LEDs and the flexible PCB.
 22. The light guide of claim 21, wherein aportion of the light guide is spirally wound.
 23. The light guide ofclaim 21, wherein a wavelength of the light emitted by the string of aplurality of LEDs is adjustable.
 24. The light guide of claim 21,wherein the plurality of LEDs are amber colored LEDs.
 25. The lightguide of claim 22, wherein the portion of the light guide is spirallywound in a first direction and includes a substantially planar portionin a second direction.
 26. A lighting device comprising: a light guide,wherein the light guide includes a plurality of light emitting diodes(LEDs) mounted on a flexible printed circuit board (PCB); and anenvelope, wherein the envelope encapsulates the light guide.
 27. Thelighting device of claim 26 further comprising a base, wherein the basecomprises at least one of a bayonet base and a screw base.
 28. Thelighting device of claim 26 further comprising electronic drivercircuitry configured to control a light intensity of the plurality ofLEDs.
 29. The lighting device of claim 28 further comprising a lightdimmer to control operation of the LEDs in a dimmed mode.
 30. Thelighting device of claim 26, wherein the lightguide is spirally wound.31. The lighting device of claim 26, wherein a wavelength of the lightemitted by the string of a plurality of LEDs is adjustable.
 32. Thelighting device of claim 26, wherein the plurality of LEDs are ambercolored LEDs.